The invention relates to the field of electronic control of rotating equipment and more particularly, to the limitation of acceleration and speed of jet engine accessory equipment when the necessary equipment is connected to a jet fuel starter system.
In the operation and maintenance of turbo jet aircraft, it is frequently advantageous to have a source of power for operating the aircraft's electrical systems while the aircraft is on the ground. This normally requires an auxiliary power source which, as separate equipment, is usually quite expensive or, in the case of military aircraft operating from advanced bases, may be awkward to provide, or even unavailable altogether. It is therefore considered highly desirable for many types of aircraft to provide a source of electrical power without the need for additional ground equipment. One approach is to utilize the aircraft's jet fuel starter, which is normally used to start the aircraft's main jet engines, to power the aircraft's accessories, including the generators. However, one drawback to this approach results from the fact that when the jet engines are disconnected from the jet fuel starter, the jet fuel starter will cause the accessories, including the generators, to accelerate at a very high rate, thus potentially causing damage to the accessory equipment. For example, constant speed drives, which are used to connect the aircraft generators to mechanical power sources such as the jet engines or the jet fuel starter, are hydro-mechanical in nature and as such are especially susceptible to damage from high acceleration rates. During a normal jet engine start operation, when the engine is connected to the jet fuel starter, the inertia of the engine will serve to reduce the acceleration rate applied to both the engine and the accessory equipment, thereby naturally maintaining the acceleration rates within desired limits. It is only when the jet engine is disconnected from the jet fuel starter that acceleration rates become excessive.